Microbiology Lecture 2. Flashcards
Pediculus humanus capitis: site, classic presentation, treatment
head lice - scalp esp behind ears; schoolgirls sharing hair accessories/winter coats; treatment = nit combing, topical insecticide, hot-wash all clothing and linens
Pediculus humanus capitis special consideration
allergic reactions to louse saliva, secondary staph infection
Pediculus humanus corporis: site, classic presentation, treatment
clothing, esp seams; shows on homeless; treatment = refer for services/improve hygiene, discard clothing
Special consideration for pediculus human corporis
can transmit typhus, trench fever, relapsing fever
Pthirus pubis: site, classic presentation, treatment
pubic hair, shows up in sluts, treatment: hot-wash all clothing, linens, shave your pubes
How can pedicures humans capitis and corporis be distinguished by pthirus pubis on microscopy?
capitis and corporis are elongated, pubis is are wide like crabs
Bacteriology of treponema pallidum
“corkscrew” motion, not culturable, slow growing, too slender for gram stain, too delicate to survive outside host
How is treponema pallidum viewed?
too small for standard microscopy, need dark field (no gram stain)
How does treponema pallidum transmit?
sexually (low infectious dose), transplacental, blood-blood
How does treponema pallidum infect after it is transmitted?
penetrates mucous membranes or small abrasions - then grows in blood vessel endothelium, enters blood and lymphatics
Primary syphilis
weeks: initial replication at site of infection, forms an ulcer, initiates bacteremia (heals in 3-12 weeks)
Secondary syphilis
months: 4-10 weeks: macropapular rash on palms and soles, moist papules on skin and mucous membranes, high infections moist lesions on genitals “condylomata lata” (come together), low fever, malaise, anorexia, weight loss, headache, myalgia, lymphadenopathy
What happens after secondary syphilis?
1/3 resolve, 1/3 enter latency (years) - early latency symptoms come and go, patient remains infections, late latency symptoms absent and not infection, 1/3 enter tertiary syphilis
Does the host raise antibodies to treponema pallidum?
yes but immunity is noncompete because surface of spirochete is nonimmunogenic and down regulates TH1 cells making antibodies useless
Tertiary syphilis
destructive stage: granulomas, CNS involvement - early meningitis, late neurosyphilis - meningovascular syphilis (popping blood vessels in brain), parenchymal neurosyphilis (tabes dorsalis and general paresis)
congenital syphilis
spirochetes easily cross placenta and survivors (50% die before birth) develop severe secondary syphilis and physical abnormalities
What is the relationship between treponema and HIV?
treponema facilitates HIV infection because ulcerations and HIV immunosuppression accelerates treponema course and reduces efficacy of treatment
What is the tell-tale sign of treponema infection?
Argyll-Robertson pupil: one or both pupils fails to constrict in response to light, but behave normally in accommodation (able to constrict on near object)
Why is diagnosing treponema difficult?
the “great imitator” - history is difficult because it can extend over years with varied symptoms developing and resolving
What lab work can be done to diagnose treponema?
microscopy: swab lesions for darkfield microscopy or IF, biopsy gummas for histology with silver or IF serology: reagin - nonspecific antibodies can be detected with cardiolipin (VDRL or RPR); specific antibodies detectable by IF or hemagglutination; NAAT
What is the treatment for treponema?
penicillin g! allergy = long-term doxycycline, erythromycin, ceftriaxone
How do you know treatment for treponema was effective?
Jarisch-Herxheimer reaction (flu like symptoms after 24h)
What will have RPR and VDRL + test results similar to treponema pallidum (syphilis)
treponema pertenue (yaws) and treponema carteum (pinta)
What is yaws and how is it treated?
treponema pertenue - tropical disease of overcrowding and poor sanitation - spread by DIRECT contact - three phases like syphilis but no neuro-cardio involvement - treat with penicillin
What is pinta and how is it treated?
treponema carateum - central and south america, no constitutional symptoms - hypo and hyper-pigmented skin plaques - spread by DIRECT contact - treat with penicillin
